


Bad Girls Get Good Grades

by Penryn3



Category: Harry Potter - J. K. Rowling
Genre: Age Difference, Bribery, Cheating, Complete, Consensual Underage Sex, Desk Sex, F/M, Infidelity, Invisibility Cloak (Harry Potter), Manipulation, One Shot, Rough Sex, Smut, Teacher-Student Relationship, Vaginal Fingering
Language: English
Status: Completed
Published: 2020-05-05
Updated: 2020-05-05
Packaged: 2021-03-02 19:08:34
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 2,018
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24021850
Author URL: https://archiveofourown.org/users/Penryn3/pseuds/Penryn3
Summary: Lily Evans had always been one of his favourites.
Relationships: Horace Slughorn/Lily Evans
Comments: 6
Kudos: 68





	Bad Girls Get Good Grades

**Author's Note:**

> Disclaimer: I do not own Harry Potter or any of the characters from it. I make no money from the writing/publishing of this story.

All of Lily’s dorm mates were asleep when she snuck out of her bed and made her way across the hall to her boyfriend's dormitory. 

_God, Gryffindor boys were disgusting._

The boys dormitories always smelled like a combination of old socks and the cloying scent of spray deodorant. She tiptoed her way through the ungodly mess in the dark, biting off a curse when she stepped on a set of old gobstones that had been left out on the floor. Reaching the third bed from the door, she knelt down and rifled through the trunk, grinning triumphantly when she felt the watery slide of the cloak slip over her fingers.

She paused, ensuring she could still hear the rumbling sound of James’s snoring through the bed hangings before standing and sweeping the cloak over herself. With any luck, she’d be back before he even knew it was gone. After all – he’d never caught her before. 

Lily cast a silencing spell on her high heeled Mary-Janes and slipped through the portrait hole, stealing through the silent corridors of Hogwarts. Arriving at the Dungeons, she made her way to Slughorn’s office door and knocked lightly. It was late, and it was a few moments before the Potions Master appeared, wearily rubbing at his eyes and stifling a yawn. He peered out at the seemingly deserted corridor in confusion before shutting the door with a shrug. She had almost let him make it back to the door that led into his bed chambers when she spoke.

“Hello, Professor,” Lily murmured in a low voice. She was amused to see Horace jump nearly a foot in the air before spinning around to gape at her sitting on the edge of his desk. His eyes widened comically.

She was wearing her school uniform, but she had made quite a few modifications to it before coming here. The button-down shirt was now straining over a black lace bra that barely contained her breasts. The scandalously short checkered skirt rode high on her thighs as she crossed one long leg over the other. Horace’s eyes flickered down to her legs and she saw his adams-apple bob as he swallowed nervously.

Lily affected a pout, all innocence as she said in her best Scarlet O’Hara voice, “I know it’s late Professor, but you see, I couldn’t sleep for worrying about my Potions final and I was wondering if there was _anything at all_ that I could do for you to make up my grade?” She was practically purring by the end of her question.

Horace Slughorn looked extremely torn. Lily saw his gaze once again rove down her body but then he shook himself slightly, straightened his spine and his voice came out stern when he said, “Now Miss Evans, I told you last time that I wouldn’t do this again. It is a breach of ethics and I really can’t stand for it any longer!” 

“What a pretty speech, Professor,” Lily said, smiling coyly. “It’s _almost_ as if you rehearsed it. Forgive me, but I found it a little…unconvincing.” 

Lily hopped off the desk and walked toward him slowly, hips swaying with every step. Horace stumbled a step back, bumping into one of the school desks. Sweat had broken out over his large shiny forehead and his eyes darted from side to side, as if trying to plan his escape route. Lily almost laughed. She might have enjoyed this game of cat and mouse if she didn’t find it all so tedious. Quite frankly, having to convince him was just eating into her hours of precious beauty sleep. 

She stopped directly in front of him, close and crowding. “The thing is Professor,” she said in a low sultry voice as she slowly unbuttoned her shirt just enough to reveal the black lace of her bra and the copious amount of cleavage it displayed. “I think you’re lying, in fact – I _know_ you’re lying.” 

Slughorn's breath hitched in his throat and he all but lay back on the desk to put distance between them. 

“I’m not,” he said weakly. “You're my student. I'm your teacher. I don’t want you like that.”

“No?” Lily asked, raising an eyebrow. She lifted one leg and placed her foot next to him on the desk. Making sure she had his attention, she trailed her fingers slowly and tauntingly up her thigh before pushing the black lace of her thong aside, stroking her fingers along her glistening folds, massaging back and forth as she let her head tilt back and her mouth fall open.

She heard a small stifled groan and opened her eyes to catch Slughorn watching her moving fingers with rapt attention. He seemed to forget himself, allowing his own hand to stray to the front of his pants – grasping his cock where it strained against the soft material. He seemed to realise this and he immediately pulled his hand away, his eyes darting up to hers, trying to gauge whether or not she had noticed the break in his control.

Lily smirked. Of course she had.

Lily pulled her fingers out of herself. Holding eye contact she brought the glistening digits up to her mouth and sucked them between her lips with a cat-like smile.

“I know you want me, Horace,” Lily purred, stepping even closer, her thighs brushing his. “You want me so very much. You're practically _gagging_ for it."

She pressed her lips to his, thrusting her tongue into his mouth and letting him taste her juices. She pulled back to observe his lust-ridden face. Lily could almost see the cracks that were appearing in his resolve as he stared at her, tongue darting out to lick his lips.

Honestly, she had to give him props for trying. 

“Still not interested?” Lily asked. “Okay then, I guess I’ll just head back to my dorm room.” She shrugged, tossing her long red hair over her shoulder and flouncing away. She was almost at his desk near the door when she ‘dropped’ her wand, letting it clatter the floor. Lily cursed loudly, bending over slowly from the waist to retrieve it. She grinned when she saw, from the view between her legs, Slughorn’s jaw go slack as he took in the sight now presented to him - Lily’s pert arse, no longer covered by her pretense of a skirt and her barley there black thong.

_Gotcha._

Lily slowly stood back up, a moment hardly passing before she felt Slughorn’s hands grabbing at her hips, propelling her forward until he was bending her over the mahogany wood of his desk - pressing his crotch to her arse as he rutted against her.

“ _Fuck_ Lily, why do you fucking do this?” He growled in her ear, reaching around her and fumbling with her shirt, ripping the buttons in his haste to get a hand clamped around her breast, his fingers eagerly twisting and pinching her nipple through the lace. Kicking her legs apart, he pressed a hand between them, impatiently pushing aside the thin fabric of her panties to thrust his meaty fingers into her. Lily could feel the moistness of his breath as he panted against her neck, his excitement building as he roughly pumped his fingers in and out of her body.

She pushed herself back onto his fingers and moaned encouragingly. Slughorn's breathing became even heavier as he moved his fingers faster, removing his other hand from her breast to fumble with his belt buckle. Seconds later she felt the naked head of him running a sticky wet line down between the globes of her arse to rub against the lips of her cunt. 

Uh…finally. Lily always made sure to makes lots of noise – moaning and screaming in all the right places. The truth was, the middle-aged man was an uninspired lover. He never tried anything new and for all his years had all the skilled talent of a fumbling over-eager schoolboy. She never really did get much out the experience, except of course getting the best potions marks in their year, despite it being her worst subject.

Lily let out another well-timed moan, wriggling her arse against him for good measure. 

“Oh Horace,” She panted, trying to sound desperate with need. Slughorn liked dirty talk, and if she got him excited enough, it didn’t last as long.

“ _Please_ Horace, I need it, I need your cock – my pussy is so wet for you...” 

Her acting was rewarded when Slughorn let out a hoarse cry and rammed his cock into her hard enough to send her hips crashing into the desk. She cried out and Slughorn let out a grunt before reefing out and slamming back in.

“Yeah, you like that dirty girl? Does your greedy wet cunt like my cock? Such a _good girl_. Good girl for taking my fat cock-” 

Lily rolled her eyes, but dutifully bucked back against him and whimpered, making sure her arse jiggled in the process. 

"Good girl, _filthy_ girl. You fucking like that? Take it - _take it-_

"Yes, Horace. _Please_ , Horace! Fuck me, _fuck me harder_!"

Slughorn lost all control then, twisting the curls of her hair in one hand and pulling, the other grasping her wrist and pressing it to the grainy wood of the desk above her head, his broad body a heavy weight against her back. His thrusts grew even harsher as he frantically plunged into her over and over again. She could feel the jerk of his cock inside her, his hips stuttering erratically as he comes with a strangled groan.

Slughorn pulled out, stumbling away from her and around the side of his desk like a drunken man, fumbling to put his softening cock back into his trousers and collapsing into the large leather desk chair.

Lily straightened with a self-satisfied smirk and performed a cleaning charm on herself before fixing her thong and doing up the remaining buttons on her shirt. She ran her fingers through her hair, smoothing out the long tresses and flipping it over her shoulder.

Slughorn looked resigned, letting out a long sigh before pulling a stack of papers out of his desk draw. He shuffled through them until he found hers and laid it on top of the pile. Even from where she was standing, Lily could clearly see the big red **T** marked on the top. Slughorn waved his wand and Lily watched as her handwriting magically jumped around the page - the letters rewording and reshuffling themselves into the correct answers. Another flick of his wrist and the red mark turned from a **T** to an **O**.

He looked at her with a peculiar expression on his face – an odd mixture of satisfaction tinged with shame. 

“You were Outstanding, as usual, Miss Evans.” He sighed. “Maybe if you put half as much effort into your studies as you did your other pursuits then you wouldn’t have to go to these lengths to ensure a passing grade.” He surmised, raising a bushy eyebrow. 

Lily gripped the arms of his chair and leaned forward, pressing her mouth to his ear. “But Professor, what fun would that be for you?” She nipped his ear playfully, and a shudder ran through Slughorn's body. When she pulled back, he was once again looking at her hungrily.

She smiled prettily. “I trust you will continue to partner me with Severus next term? No point passing the theory if my practical is dismal, is there?”

“Does that poor boy have any idea how much you’re using his affection for you?”

Lily shrugged. “What Severus doesn’t know won’t hurt him.”

“Lily, I can’t let this happen again. This is the last time I’ll do this for you.”

Lily eyed him with a small knowing smirk. It wasn’t. It never was. Lily didn’t even know why he bothered at this point. Still, they all had their games to play - she didn't care what helped him sleep at night.

She picked up the cloak and sauntered towards the door, stopping with her hand on the handle to throw him a wink over her shoulder.

“Until next time, Horace.”

**Author's Note:**

> Thank you for reading! Comments/Kudos are lovely ❤


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